This invention relates generally to the field of binding of sheets, e.g., papers, books, calendars, notebooks, cookbooks, etc. More specifically, this invention relates to a continuous filament for spiral binding a stack of sheets together as a unit. The inventive filament is formed of an elongated flexible rod-like member having an internal opening extending therethrough. The internal opening facilitates crimping of the inventive filament after it has been spiraled into a plurality of closely spaced perforations aligned along an edge of a stack of sheets. The internal opening in the filament also provides improved control over the outer dimension of the filament during manufacture.
Conventional spiral bound books, e.g, cookbooks, calendars, notebooks, tablets, etc., have been on the market for many years. The spiral binding method has commonly been used in connection with school related products but also in many other applications. Typically, a suitable length of solid wire or solid filament of suitable plastic material, e.g., polyvinyl chloride (PVC), is spirally wound through a series of closely spaced perforations along an edge of a stack of sheets. After spirally winding, the free ends of the coiled length are bent to create closures at each end to prevent unwinding of the spiral binding during use of the bound book. In bending the ends of solid wire or filaments to create these closures several drawbacks are encountered. Often, solid wire and solid filaments are difficult to bend thus requiring considerable effort and possibly additional tooling. Also, over time, such solid wire and filaments have a tendency to return to their unbent state thus promoting unwinding of the spiral binding during use. Finally, maintaining close tolerance over the outer diameter of the wire or filament over its entire length is extremely important in fabricating a filament that is suitable for spiral binding. It is exceedingly difficult to maintain control over this dimension where the wire or filament being fabricated is solid. Therefore, there is a long-felt need for a filament for use in spiral binding having closures that can be created with minimal effort and that will retain their bent configuration over time. Also, there is a long-felt need for a filament for use in spiral binding wherein it is easy to control the outer diameter over the length of the entire filament during manufacture.
There have been suggestions in the prior art for providing a wire or filament for use in spiral bound books. Representative spiral bound books are disclosed in U.S. Pat. No. 5,407,232 (DesJarlais) and U.S. Pat. No. 4,519,629 (Podosek). These books employ solid wires or filaments that are subject to the aforementioned drawbacks or deficiencies.
Representative methods and machines for spiral binding are disclosed in U.S. Pat. No. 5,584,632 (Stiles et al.); U.S. Pat. No. 5,527,141 (Malmstrom); and, U.S. Pat. No. 3,826,290 (Pfaffle).
Other patents generally disclosing hollow filaments and fibers include U.S. Pat. No. 5,585,182 (Aneja et al.); U.S. Pat. No. 4,940,617 (Baurmeister); U.S. Pat. No. 4,175,153 (Dobo et al.); U.S. Pat. No. 5,149,517 (Fain et al.); U.S. Pat. No. 4,384,022 (Fowler); U.S. Pat. No. 5,604,012 (Okamoto et al.); U.S. Pat. No. 5,604,036 (Price et al.); U.S. Pat. No. 4,129,675 (Scott); and, U.S. Pat. No. 5,405,668 (Sandt). None of the aforementioned patents describe use of a filament for spiral binding multiple sheet products nor any advantages achievable in such a spiral bound product.